They have moved out from the back of the nightwear department and onto the high street with everyone from the One Direction boys to Justin Bieber and even Rihanna rocking the all-in-one look.

Even the prime minister has pronounced on the trend declaring himself “jealous” of those worn by his children.

So what’s the attraction?

Well, a onesie is nothing if not comfy. It repels the winter chills and is perfect to wear while lolling around on the couch eating the last of the Christmas chocolates.

As daywear it’s a fashion trend for those who don’t want to have to think too hard about their clothes.

No need to co-ordinate bags or shoes and no worries about what underwear will be needed. It’s a look for the fashionably lazy.

And despite its detractors a onesie is also a cut above wearing PJs in the street – the acceptable face of nightwear as daywear.

A word of warning though girls.

Onsies might be cute.

They might be warm.

They might be easy to wear.

But they are unquestionably a passion-killer.

Kate Forrester - why I love my onesie

I’VE always been a pyjama fan.

Many a night I have got home from work at 5.45pm and been ensconced on the sofa in a fleecy dressing gown in less than 30 seconds. It’s quite a talent.

But even I had drawn a firm line at owning a onesie.

It’s just a bit weird, isn’t it? You look like an oversized baby. Or a penguin, or a tiger, or a dog, if you go for one of the “novelty” versions.

I was also a little bit scared of the onesie. My tendency towards laziness is so huge, I felt if I bought one I would never, ever get off the sofa again. Bye, swimming. Bye, bike. I don’t need you any more because my onesie hides my expanding waistline anyway.

So imagine my apprehension when I opened up a Christmas present from my mum to reveal my dream, my nightmare.

It was made of white fleece and had a hood and, more importantly, your feet were allowed to poke out the end. None of this odd babies’ booties-type stuff. It felt like the acceptable face of the onesie. I wanted to put it on IMMEDIATELY.

And so I did. It was a present and it would have been rude not to, okay?

Anyway, it’s a little bit too warm to wear in bed and don’t even get me started on the toilet logistics. But for sofa-sitting it’s the best thing ever.